Agentic Coding
Summary
Briefing: Agentic Coding For the software engineer building with AI coding agents daily
Key Insights
- The harness is now the primary optimization surface, not the model. Harness engineering—prompt structure, tool configuration, context pipeline, middleware—delivers gains that rival or exceed model upgrades. Terminal-Bench moved from 52.8% to 66.5% on the same model through prompt and middleware changes alone. JetBrains' experiment giving agents IDE-native search tools (instead of
grep/find) cut P95 latency 16% and budget overruns 33% without touching the model. Before you upgrade models, audit your tool configuration and context pipeline—the gap between a naive setup and an engineered one is larger than most model version deltas. - [AINews] The Inference Inflection
- We Gave Agents IDE-Native Search Tools. They Got Faster and Cheaper.
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[AINews] AI Engineer World's Fair — Autoresearch, Memory, World Models...
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Skills and progressive disclosure are the emerging standard for context management. "Skills"—structured markdown files with frontmatter that agents load on demand—have converged across Google (LiteRT edge), Supabase, and Addyosmani's SDLC framework as the primary abstraction for agent context. The pattern: expose only a one-line description initially; the agent loads full detail only when it determines relevance. A Supabase skill consumed ~1.3K tokens when loaded versus the full MCP tool set. The critical anti-pattern is writing skills without evals—Supabase's production experience showed a skill working correctly while the grader reported failure due to wrong success criteria, meaning untested skills are YOLO context.
- Agent Skills
- Skill Issue: How We Used AI to Make Agents Actually Good at Supabase — Pedro Rodrigues, Supabase
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TLMs: Tiny LLMs and Agents on Edge Devices with LiteRT-LM — Cormac Brick, Google
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Agent output quality is bottlenecked by human process discipline, not model capability. This is the uncomfortable finding across DORA data (AI adoption increases change fail rate), CircleCI data (main branch success at 5-year low of 70.8%), and Karpathy's formulation of "agentic engineering." The METR study found developers believed AI sped them up 20% despite a measured slowdown. Teams without strong review, testing, and planning discipline see degradation—not improvement—from agent adoption. The metrics that matter are MTTC (mean time to correct), recidivism rate, and AI review rejection rate, not story point velocity. Invest in eval infrastructure and process gates before investing more in prompt engineering.
- AI Amplifies Everything: A Team Lead's Guide to AI-Assisted Development
- Sequoia Ascent 2026 summary
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Model routing by task type has become more important than picking a single best model. The practitioner consensus is crystallizing: GPT-5.5/Codex for multi-step execution with tools (87.3% on Dingo vs. 67% for Opus 4.7), Claude Opus for blank-canvas design taste and long-context coherence, smaller Flash/Haiku variants for high-frequency tool calls where cost matters. The JetBrains IDE-search data revealed a hidden variable: Codex adopted IDE-native search tools 91% of the time while Haiku adopted them only 28%—model selection interacts with tool adoption behavior in ways most practitioners don't account for. SWE-bench saturation at 93.9% means easy coding benchmarks no longer differentiate; Terminal-Bench and PostTrainBench are the new signal.
- GPT-5.5 vs Claude vs Gemini: The Real Difference Nobody's Talking About
- Import AI 455: Automating AI Research
- We Gave Agents IDE-Native Search Tools. They Got Faster and Cheaper.
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[AINews] Agents for Everything Else: Codex for Knowledge Work, Claude for Creative Work
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A canonical production agent architecture is solidifying: planner/implementer/reviewer/merger pipelines in sandboxed environments, with issue trackers as substrate. This pattern appears independently in Sandcastle (TypeScript library for Docker-sandboxed agents), Cursor's internal architecture, and JetBrains hackathon finalists. The underappreciated insight: the reviewer agent's output is most valuable when fed back into system prompt improvement, not just used as a one-shot gate. Separately, issue trackers—with their records, state machines, explicit ownership, and queryable history—are becoming the control plane for agent systems. OpenAI's Symphony spec centers a Linear board as the agent control layer. Your work tracking choice is now your agent infrastructure choice: clean work data gives agents a head start, messy Slack threads and undocumented tribal knowledge will make agents fail exactly where you want them to help.
- I Open-Sourced My Own AFK Software Factory
- Introducing deepsec: The security harness for finding vulnerabilities in your codebase
- Anthropic Might Buy Atlassian For $40B. Here's Why It Makes Sense.
- Meet the Finalists: JetBrains x Codex Hackathon
Emerging Patterns
- Context pipelines are becoming the competitive moat, not model access. Multiple independent sources converge on this: Unblocked's production data (25 min/10M tokens with context engine vs. 2.5 hours/21M tokens without), the Terminal-Bench harness engineering results, and the explicit framing from AI Engineer World's Fair that "model quality is no longer the only meaningful moat—lock-in comes from the context pipeline." The practical implication is that organizations investing in how repo state is fetched, ranked, and compressed into prompts are building something durable, while those chasing model upgrades are on a treadmill.
- Mergeable by default: Building the context engine to save time and tokens — Peter Werry, Unblocked
- [AINews] The Other vs The Utility
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[AINews] AI Engineer World's Fair — Autoresearch, Memory, World Models...
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Agents are failing at novel optimization while succeeding at pattern completion—and this distinction determines what you should delegate. The kernel optimization hackathon provides the clearest controlled evidence: with YOLO prompting, agents produced code 5x slower than baseline (6.5ms vs 1.3ms). With context engineering, they still reverted to
Torch.mmrather than performing genuine optimization. The agent "cheated" by finding a functionally correct but suboptimal solution—a failure mode standard evals don't catch because output is correct. Meanwhile, agents excel at tasks with clear patterns in training data. The practical routing rule: delegate tasks where the desired output pattern exists in the codebase or documentation; keep humans in the loop for tasks requiring genuinely novel solutions. - How to Win Humanity's Last Hackathon - The hardest agent contest in AI.
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Building Pi, and what makes self-modifying software so fascinating
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Security attack surfaces specific to agentic coding are live, not theoretical. The Bitwarden CLI supply chain attack explicitly targeted
~/.claude.json, Cursor configs, Codex CLI, Aider, and Kiro—not just credentials. Slopsquatting (registering hallucinated package names) has 20% prevalence in AI-generated code per a 756K-sample study, with one hallucinated package spreading to 237 repositories through forks. The structural problem is that agents hold long-lived, broad-scoped credentials. Practical mitigations: pin package versions in agent-generated code, audit tools withagent-strace audit-tools, and scope tool permissions (a writing agent shouldn't have shell access). - Attackers are now targeting your AI coding tool
Dissenting Views
- The prevailing enthusiasm for AI-on-AI QA ("LLM-as-judge") is contested by production evidence. The mainstream view—echoed in Agent Skills frameworks and Supabase's eval-driven development—is that verifier agents with structured success criteria are a sound pattern for catching agent failures. The dissent comes from two directions: Brad Frost calls AI-QAing-AI "magic thinking, basically prayer," and Supabase's own production data validated his concern—a skill worked correctly but the eval reported failure because the success criteria were wrong. This isn't a reason to abandon LLM-as-judge, but it is a reason to treat it as a methodological disagreement about reliability: the technique is sound when success criteria are carefully designed and the eval framework is itself tested, but it fails silently when those conditions aren't met. The key question before deploying AI eval is: have you verified your grader's grading?
- 713: AI + Design Systems with Brad and Ian Frost
- Skill Issue: How We Used AI to Make Agents Actually Good at Supabase — Pedro Rodrigues, Supabase
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The "agents cause code quality degradation" claim has strong empirical support that practitioners optimistic about agentic coding are not sufficiently accounting for. The dominant practitioner framing treats degradation as a process failure fixable by better review gates. But the Building Pi entry—from a systems programmer directly working with 600K-line codebases—quantifies the problem: context window limits mean agents can see at most a third of a large codebase, they learn from average-quality internet code, and they produce 5-10x more errors per line than humans while lacking any "pain" incentive to refactor. DORA and CircleCI data corroborate this. The resolution may be scope-dependent: agents likely improve quality on well-defined tasks with clear contracts, and degrade quality on complex, interconnected codebases without strong architectural discipline. The disagreement is about emphasis, not facts.
- Building Pi, and what makes self-modifying software so fascinating
- Let's talk about LLMs
- AI Amplifies Everything: A Team Lead's Guide to AI-Assisted Development
Read & Act
What to read
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Agent Skills — The most deployable framework in this batch. The anti-rationalization tables, "touch only what you're asked to touch" merge-ability rule, progressive disclosure for 20-skill libraries in 5K-token slots, and five AGENTS.md non-negotiables are all implementable today. If you read one thing this week, this is it.
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Sequoia Ascent 2026 summary — Karpathy's "vibe coding raises the floor, agentic engineering raises the ceiling" framing, combined with the concrete MenuGen payment bug (plausible code, bad system design—Stripe email and Google login email can differ), reframes what it means to be a senior engineer right now. The point about "people have to be in charge of the spec and plan" has direct workflow implications that a summary can't convey.
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Skill Issue: How We Used AI to Make Agents Actually Good at Supabase — Pedro Rodrigues, Supabase — The RLS security bypass bug Claude missed, the eval failure where the skill worked but the grader said it failed, and the 1.3K token measurement for skill context consumption are the kind of production details that only appear in full. The failure modes are as important as the patterns.
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AI Amplifies Everything: A Team Lead's Guide to AI-Assisted Development — The MTTC/recidivism/regression rate metrics and the categorized AI-specific technical debt taxonomy (Initialization Debt, Load Transition Debt, Worker Queue Exhaustion, Security Surface Debt, Operational Debt) give you a measurement framework that most teams are missing. Worth reading if you're responsible for a team's AI adoption, not just your own.
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Building Pi, and what makes self-modifying software so fascinating — The strongest counterweight to the ambient optimism in most of the other sources. The "agents learning from garbage training data," "no pain = no incentive to refactor," and "complexity is their own worst enemy" arguments need to be read in full—a summary loses the force of the technical reasoning about context window limits on 600K-line codebases.
What to do
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Audit your harness before upgrading your model. Take one task you run regularly and instrument token count, latency, and budget overruns. Then make three harness changes without touching the model: (1) replace
grep/findtool calls with IDE-native or semantic search, (2) convert one key data source the agent reads from JSON to Markdown, (3) add progressive disclosure to your skills so agents see one-line descriptions first. Measure the delta. The JetBrains data suggests you'll see a 15-33% improvement in key metrics—and if you don't, you'll have learned something important about your specific workload. -
Build your eval loop for skills before you build more skills. If you're creating context files, AGENTS.md entries, or skills for your agents, implement a minimal AB test: run the same task with and without the skill, compare outputs using a simple rubric, and track whether your grader gives the same answer twice on the same output (non-determinism check). The Supabase failure—skill correct, grader wrong—is exactly what you'll encounter if you ship skills without this. The Supabase eval-driven development cycle is the right model: define metrics → create skill → run eval → grade → iterate.
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Map your codebase's agent substrate before scaling agent usage. Specifically: (1) Count PRs with "refactor" in the title over the last month—if the ratio is near zero, you're accumulating agent drift. (2) Identify which parts of your codebase have the clearest interfaces and contract boundaries—these are where agents will perform best. (3) For your issue tracker, assess whether tickets have explicit ownership, defined state machines, and queryable history—if not, fix this before adding agents that depend on it. The Atlassian/issue-tracker-as-infrastructure framing applies directly: your work data quality determines your agent integration quality.
Source Articles
- 713: AI + Design Systems with Brad and Ian Frost
- RNR 361 - Gamemaking and AI coding with Jamon Holmgren
- Sightings
- What's new in Astro - April 2026
- ⚡️ Competing with ChatGPT and Sierra, building a $10M ARR company — Yasser Elsaid, Founder, Chatbase
- Introducing deepsec: The security harness for finding vulnerabilities in your codebase
- OpenClaw Crash Course For Beginners
- Agents can now create Cloudflare accounts, buy domains, and deploy
- How To Win Humanity's Last Hackathon - The hardest agent contest in AI.
- Agent Skills
- Sequoia Ascent 2026 summary
- The Worst Coder in the World goes agentic: building a leaderboard cracking AI
- 732 bytes of Python just borked every Linux machine on earth…
- GitHub is having some major issues right now…
- Baseten CEO Tuhin Srivastava on Custom Models, and Building the Inference Cloud
- Meet the Finalists: JetBrains x Codex Hackathon
- We Gave Agents IDE-Native Search Tools. They Got Faster and Cheaper.
- The IDE Is Already an AI Quality Variable. Is It on Your AI Agenda?
- Building the Future of IDEs: Inside the First JetBrains Codex Hackathon
- Our 2026 Direction: AI and Classic Workflows in JetBrains IDEs
- I Open-Sourced My Own AFK Software Factory
- How To De-Slop A Codebase Ruined By AI (with one skill)
- LIVE: My skills are the top of GitHub Trending 😲
- Skill Issue: How We Used AI to Make Agents Actually Good at Supabase — Pedro Rodrigues, Supabase
- Ralph Loops: Build Dumb AI Loops That Ship — Chris Parsons, Cherrypick
- TLMs: Tiny LLMs and Agents on Edge Devices with LiteRT-LM — Cormac Brick, Google
- Mergeable by default: Building the context engine to save time and tokens — Peter Werry, Unblocked
- Context Is the New Code — Patrick Debois, Tessl
- Human-in-the-Loop Automation with n8n — Liam McGarrigle
- Software Engineering Is Becoming Plan and Review — Louis Knight-Webb, Vibe Kanban
- Agents on the Canvas in tldraw — Steve Ruiz, tldraw
- Shipping complex AI applications — Braintrust & Trainline
- Agents for Everything Else — swyx
- Building Conversational Agents — Thor Schaeff and Philipp Schmid, Google DeepMind
- LLM codegen fails and how to stop 'em — Danilo Campos, PostHog
- Replacing 12K LoC with a 200 LoC Skill — David Gomes, Cursor
- OpenAI Codex Masterclass — Vaibhav Srivastav & Katia Gil Guzman
- Build & deploy AI-powered apps — Paige Bailey, Google DeepMind
- Building your own software factory — Eric Zakariasson, Cursor
- Why building eval platforms is hard — Phil Hetzel, Braintrust
- One Login to Rule Them All: Cross-App Access for MCP — Garrett Galow, WorkOS
- GPT-5.5 VERIFIED Opus 4.7: A Pi Coding Agent That REVIEWS Like YOU
- Box CEO on AI Agents & Why Enterprise Can't Keep Up | a16z
- Seriously, Anthropic??
- Is GitHub going to die now?
- Claude Code's favorite tech stack
- Claude Jupiter 🤖, Codex pets 🐾, Replit’s margin lead 📈
- Claude Cowork: Build Your Own Jarvis
- 🎙️ This week on How I AI: The internal AI tool that’s transforming how Stripe designs products
- Shipping todometer, version 3!
- AI Amplifies Everything: A Team Lead’s Guide to AI-Assisted Development
- AI-Assisted Coding: A Practical Guide for Software Engineers
- [AINews] The Other vs The Utility
- [AINews] AI Engineer World's Fair — Autoresearch, Memory, World Models, Tokenmaxxing, Agentic Commerce, and Vertical AI Call for Speakers
- [AINews] Agents for Everything Else: Codex for Knowledge Work, Claude for Creative Work
- [AINews] The Inference Inflection
- [AINews] not much happened today
- What the Agent Economy Looks Like From Inside Stripe
- GitHub Copilot CLI for Beginners: Interactive v. non-interactive mode
- Open-Weight AI Models
- Let's talk about LLMs
- I am worried about Bun
- Redis array: short story of a long development process
- This One Skill Fixes AI Codebases
- Are AI Coding Skills Just Hype? I Tested Them
- This Claude Skill Saves Me Hours on Every Landing Page
- I Didn’t Expect This: Opus 4.7 vs GPT 5.5
- This Claude Skill Handles Your Entire PR For You
- Stop Watching AI News. Go Build Something.
- AI Agents are briefly overhyped
- Why We Need Continual Learning
- Building a Natural Language Interface to the Spotify Ads API with Claude Code Plugins
- Import AI 455: Automating AI Research
- Anthropic Might Buy Atlassian For $40B. Here's Why It Makes Sense.
- RTX 5090, Mac Studio, or DGX Spark? I tried all three.
- Microsoft Is Testing Claude Against Its Own Copilot. Here's Why.
- Salesforce Killed The Browser. Every Agent Runs Your CRM Now.
- GPT-5.5 vs Claude vs Gemini: The Real Difference Nobody's Talking About
- AI era skills: Why cultivating agency matters more than job titles | Max Schoening (Notion)
- Building Pi, and what makes self-modifying software so fascinating
- I built an AI agent that orders food for your entire team
- Attackers are now targeting your AI coding tool
- How to Improve at Sensemaking AI?
- OpenAI Workspace Agents 101: Build, Run, and Scale AI Workflows
- briefing 2026-04-14T05:00:49.370475+00:00
- briefing 2026-04-11T01:59:24.670464+00:00